Coop DeRenne: a Man Whose Message Goes Largely Unheeded

As a baseball athlete as well as a athletic development coach I can remember hearing Coop DeRenne speak nearly 20 years ago on the subject of weighted implement training as a tool for striking/hitting sports like baseball, tennis, golf and the like.
Though his research has been largely in baseball at the Univ. of Hawaii the principles apply to virtually all ball and stick sports as it were: hockey, golf, racquet sports, baseball, etc.
DeRenne's research has shown that there is a very finite window in which you can use a weighted implement similar to the one in your chosen sport without throwing off the finely honed coordination of that skill.
In baseball, for example, it is common for players in the on-deck circle to swing all manner of weighted objects some of which bear little to no resemblance to a bat: steel bars, re-rod, lead bats, etc.
DeRenne's research has indicated that this practice, steeped in baseball myth/superstition, has no basis in science. His studies have shown the invariably bat speed actually slows down when using these tools for warming up and does the opposite and what the player thinks they are doing for him/her.
The window for this type of training is very narrow, =/- 10% to be exact. So if you are swinging a 30 ounce bat, an average weight for many college and pro players, then your "practice" bat should weigh no more than 33 ounces or less than 30 ounces if you don't want to screw up your swing mechanics. The same principles apply to weighted baseballs as well.
These concepts would apply to golf swing mechanics which are also a finely tuned and precise pattern where the slightest variation can cause things to go awry.
So this is one of those situations where just because they done it that way for a long time doesn't mean it's right or helpful. In this case it's the opposite.
But baseball let's go of it's traditions very slowly, if at all, despite all the evidence to the contrary in many cases. Do don't expect major league on-deck circles do to without the usual warmup "tools": weighted donuts and sleeves, lead bats and the occasional random piece of steel!

Train hard and train smart!
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